Researchers at Harvard University recently invented a new process that can make glass change colors by tuning voltage. It isn’t the first time researchers try to develop color-tunable glass.  However, they all adopted the costly electrochemical reaction method in order to achieve the transition. The new technology developed by Harvard team has found a way to adjust the transparency of the window glass by changing the geometrical arrangement of the material.

Researchers at Harvard’s School of Engineering and Applied Sciences have described it in a paper published in the latest journal Optics Letters. Their tunable glass is made from a sheet of glass sandwiched between two layers of transparent, soft elastomer. The elastomer has been sprayed with a coating of silver nanowires. The nanowires are tiny in size and don't scatter light. But things change when you apply an external electric voltage.

Upon the application of voltage, the two nanowire layers get the energy to move nanowires closer to each other and causes the elastomer to deform. While the silver nanowires are scattered randomly, the elastomer also deform unevenly. This uneven surface scatters light, making the glass surface cloudy. The important thing is that the entire transition takes less than a second, said the researchers. They also found that the roughness of the elastomer surface is related to the voltage applied. The higher the voltage applied, the rougher the surface gets and eventually turns the glass opaque.